Even more profoundly dramatic were Conrad’s experiences in the Congo where his seafaring skills gave him personal exposure to one of the most dark and secretive projects of the nineteenth century: the staking of the Congo River basin as the private property of Leopold II, King of the Belgians. It is important to remember that when the Congo Free State was founded in 1885 it was not a colony in the traditional sense of the word, claimed by an entire European nation. Instead the million square miles of rainforest, savannah, swamp and waterway were staked by a single man, King Leopold, the largest private estate in history.

But it was not just an exercise in vanity on an unimaginable scale. It also involved unfathomable cruelty. Publicly, the founding of the Congo Free State was presented as an act of enlightenment, of taming wilderness and bringing civilisation, Christianity and commerce to a place of primitive savagery. In reality, much darker forces were at work, as the king’s colonial agents set tribe against tribe in pursuit of plunder; first ivory, later raw rubber.

Under King Leopold’s aegis the first genocide of the modern era was committed. Millions of Congolese were slaughtered to generate revenue for the king across the water. They died in the ethnic cleansing and battles of frontier wars fought between Leopold’s agents and Arab slavers who had been in the eastern Congo much longer than white outsiders and were not happy to be usurped. But once the Arab slavers had been defeated, Congolese tribes were persecuted brutally pour encourager les autres. Colonial agents invented a uniquely vile if apparently counter-intuitive way of making Congolese villagers increase their production of goods – the agents would have the hands of prisoners hacked off to show what happens to the disobedient. The best estimate is that between three and ten million Congolese were killed in just over two decades starting in 1885.

What made the project all the more sinister was the way it was hidden from the outside world. Private companies in Belgium acted as fronts for King Leopold, carefully selecting those who would be employed in the Congo Free State and ensuring its true nature stayed hidden. Any European explorer or adventurer who ventured into the Congo Free State without signing up as an employee of one of these companies was hounded out, persecuted, even murdered. And throughout, the illusion of a civilising act of philanthropy was maintained to the outside world.

For a short time Conrad became personally involved in this sinister project. He did not just witness what was going on in the Congo, he became part of the whole colonial exercise. This made him complicit with one of the greatest ever crimes against humanity and Conrad’s inevitable feelings of personal guilt must be considered when trying to understand how Heart of Darkness came to be written. Conrad’s involvement only lasted a few months but he became, essentially, a hired hand of King Leopold. It was in the early days of the Congo Free State when the king’s agents were crying out for people who knew about boats. The equatorial rainforest that covered much of the territory was almost impenetrable and it made good practical sense to make use of Africa’s mightiest waterway, the Congo River, and its web of tributaries that covered an area the size of the Indian subcontinent.